The present invention relates to a method and apparatus for water sanitisation. The invention will primarily be described with reference to its use to provide sanitisation of swimming pool water containing bacteria, algae and other water-borne diseases, but it should be remembered that the invention can have broader applications to any other body of water which may contain such organisms and diseases and which therefore require sanitisation.
This application claims the priority of Australian patent application Serial No. PP 2161 filed on Mar. 5, 1998.
Although chlorine and other halogens are the preferred method of water sanitisation, it is well known that this method has a number of drawbacks. xe2x80x9cSuperchlorinationxe2x80x9d of pools (where the concentration of chlorine in solution exceeds 10 ppm) is scientifically the recommended requirement to sanitise water to meet the requirements of health regulations even though all halogens, and especially so chlorine, are highly reactive elements and readily form by-products, which themselves can be known dangerous environmental pollutants and proven carcinogens. Chlorine itself is highly toxic for human beings, and health authorities only permit certain levels of chlorine in swimming pool water (typically 2-3 ppm). Consumption or degradation of the chlorine through normal usage of the swimming pool can cause a breakdown in the effectiveness of the sanitisation process. In summary, current methods of sanitisation using halogens alone are crude, not fully successful at eliminating disease organisms, and highly dangerous from an occupational health standpoint since the reagents used for effective sanitisation are extremely toxic.
Chlorine forms hypochlorous acid with water under certain circumstances. It is well known that approximately 80% of available chlorine ions are converted to hypochlorous acid if the water pH is around 6.8. At a water pH of around 8.0 only 20% of the available chlorine is converted to hypochlorous acid.
Hypochlorous acid is approximately 300 times more effective as a sanitiser than chlorine, and it does not form dangerous by-products. For instance, it is known that hydrogen peroxide is a natural product of human body cells. In combination with available chlorine (from body salt intake), the hydrogen peroxide will form hypochlorous acid, constituting a disease control mechanism in the cell environment.
Hypochlorous acid formation by means of addition of chlorine and hydrogen peroxide reagents is thus much more environmentally friendly and less dangerous to the users of swimming pools than other materials used for sanitisation such as chlorine, bromine and iodine. Concentrations of hypochlorous acid can be kept at relatively high levels giving better health protection for users of the swimming pool. It has become usual to identify a preferred operating range of redox potential (ORP) for the water being sanitised of 220-290 mV, more preferably 235-275 mV when the correct relative amounts of hydrogen peroxide and halogen are present.
All of the abovementioned features have been disclosed in our Australian Patent AU657897. Currently, health authorities worldwide are seeking methods to realize even lower concentrations of disease-causing organisms and means to keep bacteria under control more effectively with minimum exposure of water users to halogen reagents, combined with effective conversion of hydrogen peroxide and halogens to hypohalous acid.
Although the use of ionic species such as copper and silver salt ions are known concommitant additives to improve the performance of a water sanitisation process using a hydrogen peroxide and chlorine, as disclosed in WO 98/22397, such systems rely on the release of dangerous toxins into water systems, such as Cu2xe2x88x92 ions, along with high concentrations of chlorine released locally into the water body in the vicinity of the additive pellets described therein. Ions such as Cu2xe2x88x92 ant Agxe2x88x92 are very poisonous to living creatures including man. Direct release of such species into a water system in an essentially uncontrolled manner can be unsafe practice, both for water users and a dangerous procedure for operators.
The present invention in a first aspect provides a method of sanitising a body of water by:
(a) adding an amount of hydrogen peroxide predetermined by the volume of water to be sanitised, and
(b) adding an amount of halogen predetermined by the volume of water to be sanitised, and
(c) adding an amount of one or more of the group comprising silver and copper as colloidal dissolved metals produced by the controlled dissolution of the corresponding metallic source metals under the action of hydrogen peroxide and halogen present in the water to be sanitised, and
(d) wherein the amount of hydrogen peroxide is so predetermined to ensure that all halogen is converted to hypohalous acid and sufficient hydrogen peroxide is left over to provide at least some oxygenation of the water.
Preferably the water sanitisation method includes the use of a reticulation pump for providing a flow of water requiring sanitisation, and a container arranged to receive water under pressure from said pump, said container being adapted to contain sources of said colloidal dissolved metals and halogen reagent, whereby said water is recirculated through said container and returned to the flow of water, and wherein, upstream from where said container receives water from said pump, metering means are arranged to deliver hydrogen peroxide reagent into the flow of water.
Preferably the water sanitisation method provides for said water to be returned to the flow of water downstream of the delivery of hydrogen peroxide reagent into the flow of water.
Preferably the water sanitisation method provides for the flow of water to said container from the pressure side of the pump to be regulated by constriction in order to allow an appropriate residence time of fluid in the container for effective chemical reactions to occur.
Preferably the water sanitisation method provides for the rate of hydrogen peroxide reagent delivery to be adjusted to suit the particular conditions of sanitisation required and the flow rate of water for treatment.
In a further aspect, the present invention provides apparatus for sanitising a flow of water recirculated from a body of water by a pump having an inlet conduit and an outlet conduit both in communication with the body of water, said apparatus comprising a container adapted to hold sources of one or more of the group comprising silver and copper as colloidal dissolved metals and a source of halogen reagent, a feed conduit extending from the container and adapted to be connected to the outlet conduit, a return conduit adapted to be connected to one of the inlet conduit and the outlet conduit, such that in use water under pressure from the pump passes through the feed conduit, the container, and the return conduit, said apparatus further comprising metering means adapted to deliver hydrogen peroxide reagent into the flow of water upstream of the connection of the feed conduit to the outlet conduit.
Preferably the apparatus for sanitising water has metering means comprising a solenoid valve or metering pump or the like, adapted to deliver hydrogen peroxide reagent at a pre-determined rate into the flow of water upstream of the pump.
Preferably the apparatus for sanitising water has a pump associated with a coarse filter, wherein the return conduit is connected to the inlet conduit upstream of the coarse filter.
Preferably the apparatus for sanitising water has a container adapted to include sources of metallic copper and silver and halogen reagent in which the metallic copper and silver are present as a plurality of metallic bars, rods or granules, and sources of chloride are present in solid form.